When reading a document using an image reading apparatus, image copying apparatus, or the like, if an edge portion of the document is folded or torn, the document backing surface will show up in such an edge portion when the document is read. If, for example, the background color of the document is different from the color of the document backing surface, the region in the stored image data or copied document where the document backing surface shows up can become distracting to the eye. If such region are to be corrected, document edges must be accurately detected from the readout image.
There is disclosed an image editing apparatus that detects solid black portions in image data read from a document image, and that, if there is any solid black portion in the position specified by the user using a specifying means, then erases the solid black portion (refer to Japanese Laid-open Patent Publication No. 9-172534).
There is also disclosed an image processing apparatus that detects black frame regions at both ends of a readout document and removes the black frame regions. This image processing apparatus holds image data of the readout document on a line-by-line basis, and detects a continuous black pixel region continuing from the reading start position, with provisions made to reset any previously detected black pixels each time a white pixels appears, and then detects the finally left continuous black pixel region (refer to Japanese Laid-open Patent Publication No. 2000-354150).